Portable and adaptive specification of disk bandwidth quality of service

Continuous media (CM) applications require Quality of Service (QoS) guarantees from the disk, as well as from the CPU and network. Their requirements can often be expressed in terms of data rates, which are portable descriptions of resource needs. QoS-aware disk schedulers need an accurate predictor of their clients’ resource usage in order to perform admission control and limit the effect of misbehaving clients. We present a scheme which allows the client to directly specify its desired data rate to the scheduler. A per-client time limit bounds the amount of time spent trying to achieve this rate. By using feedback from the scheduler, the client can renegotiate its time limit. The result is a simple and adaptive method of determining resource requirements.